Influence of Impurity of MgO Substrates on Properties of Molecular Beam Epitaxy-Grown Superconducting NdBa₂Cu₃O_7-δ Thin Films

Abstract

Classical mechanics has been applied in the theoretical study of the ionization of hydrogen atoms by static electric and circularly polarized electromagnetic fields. In both cases it was assumed that the ionizing field was adiabatically switched on. In the case of circular fields the calculations were performed for the initial energies E 0 = −1/2n 2 0 and frequencies of the field ω for which ωn 3 0 0.44. For such initial conditions almost all trajectories that lead to ionization are regular. The results of adiabatic theory and numerical simulations are compared with recent experiments.

Coherent growth of superconducting TiN thin films by plasma enhanced molecular beam epitaxy

“…High quality (001) MgO substrates with low Ca impurity levels of less than 250 ppm have been used to minimize contamination by segregated Ca. 8 The MgO substrates were annealed for 12 h in flowing oxygen at 1000 C prior to the introduction into the ultra-high vacuum (UHV) chamber. The growth temperature T growth was varied from 520 C to 720 C, which was monitored by an optical pyrometer.…”

Ab initiotypical medium theory of substitutional disorder

“…Deviations from perfect crystallinity in MgO can have detrimental effects on its functionality. It was shown that poor-quality MgO substrates gives rise to poor-quality thin films 70 , while defects and impurities can lead to a degradation of the superconducting properties in high-T c superconductors 72,75 . On the other hand it is known that doping Fe/MgO/Fe tunnel junctions with carbon impurities increases the output voltage and reduces noise 76,77 .…”